1. Field of the Invention
The invention relates to a converter control system, and more particularly to the converter control system that introduces digital circuits to control and adjust duty cycles according to the light-load status and the heavy-load status.
2. Description of the Prior Art
With progress in modern technology, various electronic devices have become necessities to people's daily life. Also, as rising demands in energy saving and environment preservation upon consumer electronics, low power consumption for an idle state of the electronic product so as to extend service life of batteries and to reduce the consumption of electricity has been one of basic requirements for designing a converter in this industry.
Referring to FIG. 1, a schematic view of a conventional power converter (a flyback converter) is shown. Generally, this flyback converter includes an analog pulse width modulation (PWM) control switch module PA1 and a converter PA2. The converter PA2 electrically coupled with the analog PWM control switch module PA1 generally includes a bridge rectifier PA21, a transformer PA22, a filter circuit PA23, a load switch PA24, a feedback circuit PA25, a compensation circuit PA26 and a load resistor PA27. The transformer PA22 is electrically coupled with the bridge rectifier PA21 and the filter circuit PA23. The load switch PA24 is electrically coupled with the transformer PA22 and the load resistor PA27. The feedback circuit PA25 is electrically coupled with the filter circuit PA23 and the compensation circuit PA26. In addition, the compensation circuit PA26 is electrically coupled with the analog PWM control switch module PA1.
In this conventional design, the analog PWM control switch module PA1 bases on the load status to control the load switch PA24 to be switched on or off. The analog PWM control switch module PA1 electrically coupled with the converter PA2 can be mainly consisted of a leading edge blanking (LEB) circuit, an oscillator, an error amplifier, a latch circuit and a comparator. However, in general, this type of the analog circuit usually lacks of design flexibility. In practice, in the case that the converter PA2 is operated in a continuous conduction mode (CCM), a discontinuous conduction mode (DCM) or a boundary conduction mode (BCM) so that a revised circuit is needed, the revision work would be confined to the framework of the analog circuit, and thus the re-programming would be hard to performed. Hence, a new design for the internal circuit and the compensation circuit PA26 would be necessary, from which direct applicability would be poor.